1. Field of the Invention
The present invention relates to an electronic device for enhancing image quality of a liquid crystal display (LCD) monitor and related method and LCD monitor, and more particularly, to an electronic device and related method and LCD monitor capable of prolonging time of a scan line signal output circuit driving a panel when the LCD monitor is turned off, to avoid residual images, blinking situation, etc when the LCD monitor is turned on again, so as to enhance image quality of the LCD monitor.
2. Description of the Prior Art
A liquid crystal display (LCD) monitor, featuring slim design, low power consumption, and no radiation pollution, has been applied widely to a computer system, a mobile phone, a Personal Digital Assistant (PDA) and so on. The operation principle of an LCD monitor is based on different alignments of liquid crystal molecules with different effects of polarization and deflection. By means of different alignments of the liquid crystal molecules, the light can be allowed to pass through in varying amount, thus constituting different intensities of the emitting light and different levels of grayscales in red, blue and green.
Please refer to FIG. 1, which is a schematic diagram of a thin film transistor (TFT) LCD monitor 10 according to the prior art. The LCD monitor 10 includes an LCD panel 100, a timing control circuit 102, a data line signal output circuit 104, a scan line signal output circuit 106, and a common voltage generator 108. The LCD panel 100 includes two substrates with liquid crystal material in between. One substrate has a plurality of data lines 110, a plurality of scan lines (gate lines) 112 perpendicular to the data lines 110, and a plurality of TFTs 114. Another substrate has a common electrode for providing a common voltage Vcom via the common voltage generator 108. For convenient explanation, only four TFTs 114 are shown in FIG. 1. There exists one TFT 114 at every intersection of each of the plurality of data lines 110 and scan lines 112 in practice. In other words, the TFTs 114 are distributed on the LCD panel 100 in matrix. Each data line 110 corresponds to a column of the LCD monitor 10, each scan line 112 corresponds to a row of the LCD monitor 10, and each TFT 114 corresponds to a pixel. Furthermore, the circuit characteristic of the two substrates of the LCD monitor 10 is regarded as an equivalent capacitor 116.
In the LCD monitor 10, the timing control circuit 102 generates control signals for the data line signal output circuit 104 and the scan line signal output circuit 106 respectively, and thus the data line signal output circuit 104 and the scan line signal output circuit 106 generate input signals for different data lines 110 and scan lines 112, so as to control conduction of the TFTs 114 and voltage difference of the equivalent capacitor 116, and change alignments of the liquid crystal molecules and the light transmittance, to show display data 122 on the LCD panel 100. For example, the scan line signal output circuit 106 inputs a pulse into the scan lines 112, to conduct the TFTs 114. Therefore, the input signals generated by the data line signal output circuit 104 are inputted into the equivalent capacitor 116 through the TFTs 114, so as to control the gray level status of the related pixel. In addition, a level of the input signals outputted from the data line signal output circuit 104 to the data lines 110 can generate different gray level.
Since a circuit characteristic of the liquid crystal is similar to a capacitor, the equivalent capacitor 116 stores charges with different coulombs during an operation process of the LCD monitor 10. If the charges stored in the equivalent capacitor 116 can not be released efficaciously when the LCD monitor 10 is tuned off, the LCD panel 100 generates residual images, blinking situation, etc when the LCD monitor 10 is turned on again, to affect image quality of the LCD monitor 10. Therefore, in order to solve above problems, the LCD monitor 10 of the prior art has a scheme of releasing residual charges when turned off the LCD monitor 10. Please refer to FIG. 2 for a detailed description.
Please refer to FIG. 2, which is a schematic diagram of the timing control circuit 102 of FIG. 1 when controlling the scan line signal output circuit 106 to release residual charges. An implement of releasing residual charges is that the timing control circuit 102 outputs a start indication signal XON into the scan line signal output circuit 106, and an output indication signal VGH into the scan lines 112 to output a high voltage level voltage (or a voltage value of the output indication signal VGH). The output indication signal VGH is generated by an output indication signal generator 124 (such as system power generator), and is a high voltage level signal for controlling an output state of the scan line signal output circuit 106, so as to turn on the TFTs 114 at a proper time. When the output indication signal VGH is at high voltage level, the TFTs 114 are turned on, and when the output indication signal VGH is at low voltage level, the TFTs 114 are turned off. The start indication signal XON is utilized for indicating an operation state of the scan line signal output circuit 106. When the start indication signal XON is at high voltage level, the LCD monitor 10 is in an ON state, and when the start indication signal XON is at low voltage level, the LCD monitor 10 is in an OFF state. An operation procedure of releasing residual charges is described as follows. First, when the LCD monitor 10 is turned on, and has not been turned off (before a time point T1), the output indication signal VGH and the start indication signal XON are at high voltage level. When the LCD monitor 10 is turned off by a user or system control (at the time point T1), the voltage level of the start indication signal XON transits to low voltage level instantaneously. After a delay duration, the voltage level of the output indication signal VGH is getting small, and finally becomes a ground voltage GND at a time point T2. In a process of the output indication signal VGH from high voltage level to low voltage level (meaning from the time point T1 to T2), the scan line signal output circuit 106 keeps outputting high voltage level voltage to charge the TFTs 114, so as to release the residual charges of the equivalent capacitor 116. However, if time between the time point T1 and T2 is not sufficient, the residual charges of the equivalent capacitor 116 cannot be released completely, and thus when the LCD monitors 10 is turned on again, the LCD panel 100 has residual images, blinking situation, etc, causing degradation of image quality.
In a word, when the LCD monitor 10 of the prior art is turned off, if time of the scan line signal output circuit 106 charging the TFTs 114 is not sufficient, the residual charges of the equivalent capacitor 116 cannot be released completely. Therefore, when the LCD monitor 10 is turned on again, the LCD panel 100 generates residual images, blinking situation, etc, and thus affects image quality.